Tamper Indicating Labels with Planar Ingress Solvent-Indicating Feature

ABSTRACT

Tamper- and solvent-indicating labels comprise a single layer of a solvent-indicating composition over and in contact with a tamper-indicating label. The composition of the solvent-indicating label is sensitive to solvent (e.g., water, hydrocarbon, etc.). If the label is designed for sensitivity to water, then it typically comprises an organic solvent-soluble binder, pigment at a concentration greater than the critical pigment-binder ratio, and dispersed water-soluble dye particles. The tamper-indicating label can be of any construction, e.g., frangible and difficult to remove, or easy to remove but leaving behind a pattern of adhesion, or cleanly removed but irreversibly changed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. provisional application Nos. 60/870,271 and 60/885,710 filed Dec. 15, 2006 and Jan. 19, 2007, respectively.

FIELD OF THE INVENTION

This invention relates to labels. In one aspect, the invention relates to tamper-evident labels while in another aspect, the invention relates to tamper-evident labels with a planar ingress solvent-indicating feature. In still another aspect, the invention relates to an electronic device bearing a tamper-evident label with a planar ingress solvent indicating feature while yet in another aspect, the invention relates to a method of visibly recording the exposure of an electronic device to solvent.

BACKGROUND OF THE INVENTION

Solvents, i.e., liquid water and/or an organic solvent such as a hydrocarbon or halogenated hydrocarbon, e.g., gasoline, turpentine, chloroform, perchloroethylene, etc., can readily damage electronic devices such as laptop computers, cell phones and personal digital assistants. Accordingly, a need exists for a label or other device to indicate whether or not an electronic device has been subjected to contact with a solvent, at least sufficient solvent to void a product warranty. This need is filled to some extent by various commercially available, single-purpose labels with a format as described in FIG. 1.

As shown in FIG. 1, solvent (here water) indicating label 10 comprises four layers. First or top layer 11 is typically a water-impervious clear plastic film, e.g., a clear polyester film, overlying water-absorbent paper layer 12. Underlying layer 12 is a layer of water-soluble ink (or dye) 13 which itself overlays a pressure sensitive adhesive layer 14. The water-soluble ink is not visible through the paper until wetted.

Water enters the structure from an edge surface of the label, not a face surface or in other words, the structure is an edge ingress label. If an edge surface of the label comes in contact with liquid water, then water will wick along the paper layer dissolving the water-soluble ink beneath the paper layer. The paper layer will absorb the solubilized ink, and the ink will become visible to an observer. The clear plastic film protects the label and keeps dissolved ink from seeping to the surface of the label and contaminating the electronic device and/or marking the user's person or clothing. If, of course, an organic solvent-soluble ink replaces the water-soluble ink, then this label will detect and report contact of the label with the organic solvent, not water.

While these single-purpose labels perform as designed, a strong interest in the electronic device industry exists for a label that can perform more. For example, an unscrupulous person could remove an activated water-indicating label from a device that has been in contact with liquid water, and replace it with an unactivated water-indicating label. One label that had both water- and tamper-indicating features could report such activity. The use of separate labels for each function would not report such activity and in any event, surface space on many electronic devices is limited thus making a dual or multi-purpose label more desirable than two or more separate labels.

One approach to a dual purpose label is to attach a small solvent-indicating label to a larger tamper-indicating label, but this approach has several drawbacks. First, the solvent-indicating label takes space on an already small label, and that space could be better used for printed information, e.g., a bar code. Second, a roll of labels with non-uniform thickness is difficult to roll uniformly. Third, the thicker portion of the label creates difficulties if print is imparted to the label using thermal transfer printing. Fourth, such a label with another label creates a very thick profile and interferes with efficient packing of a battery and other components into a thin electronic device.

Better solutions and improved formats are desired for an effective label that possesses both tamper- and solvent-indicating features.

SUMMARY OF THE INVENTION

In one embodiment, the invention is a multi-layer, planar ingress tamper- and solvent-indicating label comprising a single layer of a solvent-indicating composition coated over a tamper-indicating label. The composition of the solvent-indicating label is porous to solvent, and it comprises an organic solvent-soluble binder, pigment at a concentration greater than the critical pigment-binder ratio, and dispersed solvent (typically water) soluble dye particles. The tamper-indicating label can be of any construction, e.g., frangible and difficult to remove, or easy to remove but leaving behind a pattern of adhesion, or cleanly removed but irreversibly changed.

In another embodiment, the invention is a multi-layer, planar ingress tamper- and solvent-indicating label comprising a tamper-indicating label, a composition porous to solvent and coated over the label, and an ink applied as indicia, typically in a single printing pass, over the composition. The tamper-indicating label can be of any construction, the composition comprises an organic solvent-soluble binder and pigment at a concentration greater than the critical pigment-binder ratio, and the ink comprises a solvent (typically water) soluble dye.

In another embodiment, the invention is a multi-layer, planar ingress tamper- and solvent-indicating label comprising a tamper-indicating label, a composition porous to solvent and coated over the label, and a crosslinked polymer film (through which solvent can migrate) coated or laminated to the composition. If the solvent-indicating label is a water-indicating label, the crosslinked polymer is hydrophilic. The tamper-indicating label can be of any construction, the composition comprises an organic solvent-soluble binder and pigment at a concentration greater than the critical pigment-binder ratio and dispersed solvent (typically water) soluble dye particles, and the crosslinked polymer film can absorb and transmit solvent while still maintaining integrity as a continuous layer. For water-indicating labels, one film that can serve these functions is polyvinyl(alcohol) crosslinked with aziridine.

In another embodiment, the invention is a multi-layer, planar ingress tamper- and solvent-indicating label comprising (A) a tamper-indicating label, (B) a composition coated over the label to form a first layer that is non-porous to solvent, (C) a second layer coated over the first layer and comprising an organic solvent-soluble binder, dispersed solvent (typically water) soluble dye particles, and (D) a crosslinked polymer film coated over the second layer that can absorb and transmit solvent while still maintaining integrity as a continuous layer. In operation, solvent comes in contact with the dye particles in the second layer, and dissolves the dye particles. The soluble dye then is trapped in or below the crosslinked polymer film staining it to produce a permanent color.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view of a single-purpose water-indicating label known in the art.

FIG. 2A is a schematic cross-sectional view of a tamper- and water-indicating label in which a tamper-indicating label is coated with a water-indicating composition.

FIG. 2B is a schematic cross-sectional view of a tamper- and water-indicating label in which a tamper-indicating label is coated with a water-indicating composition that bears ink applied as indicia.

FIG. 2C is a schematic cross-sectional view of a tamper- and water-indicating label in which a tamper-indicating label is coated with a water-porous, water-indicating composition that is coated or laminated with a crosslinked hydrophilic polymer.

FIG. 2D is a schematic cross-sectional view of a tamper-and water-indicating label in which a tamper-indicating label is coated with a non-water porous composition comprising a dispersed water-soluble dye, which in turn is coated with a crosslinked hydrophilic polymer.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

“Tamper-indicating label”, “tamper-evident label” and like terms mean a label that provides evidence that the label was removed, or an attempt was made to remove the label, from the substrate to which it was attached. The evidence is usually visible to the unaided human eye, and the evidence can be on the substrate, label or both.

“Solvent-indicating label”, “solvent-evident label” and like terms mean a label that provides evidence that it was in contact with a solvent. The evidence is usually visible to the unaided human eye, and the evidence is typically confined to the label itself.

“Tamper- and solvent-indicating label” and like terms mean that a label provides evidence that it was removed, or an attempt was made to remove it, from a substrate, and that it provides evidence that it was in contact with a solvent.

“Planar ingress label”, “planar ingress, multi-layer tamper- and solvent-indicating label” and like terms mean a label into which solvent enters primarily, if not exclusively, through a planar for facial or top) surface. Planar, or facial or top ingress is used in distinction to edge ingress in which solvent enters the label primarily, if not exclusively, through an edge surface.

“Solvent-soluble” and like terms mean that a material, e.g., dye, ink, etc., will at least partially dissolve, i.e., enter solution, in a solvent (e.g., water, or an organic compound, or a mixture of water and an organic compound such as water and an alcohol).

“Solvent” and like terms mean a substance that is capable of dissolving another substance (i.e., a solute) to form an essentially uniformly dispersed mixture (i.e., solution) at the molecular or ionic size level. Solvents include water and organic compounds. In the context of this invention, the solvents are typically liquid but can be a gas, e.g, steam.

“Organic solvent” and like terms mean a solvent other than water, e.g., a hydrocarbon or oxygenated or halogenated hydrocarbon such as gasoline, turpentine, chloroform, perchloroethylene, acetone, alcohol and the like.

“Dye” and like terms mean a visible light absorbing compound that is present in a molecularly dispersed (dissolved) form.

“Ink” and like terms mean a coatable or printable formulation containing a dye and/or pigment.

“Pigment” and like terms mean a visible light absorbing material or compound that is present in a non-molecularly dispersed (particulate) form.

“Binder” and like terms mean a film- or matrix-forming material in which dye or pigment particles are dispersed. Usually these materials are solvent polymers that exhibit adhesive properties towards fillers, dyes, pigments and the like. Representative of these materials are drying or mineral oils, and polymeric substances such as alkyd resins, acrylates and methacrylates, polyvinyl alcohol, ethyl vinyl acetate, etc.

“Planar surface”, “facial surface”, “top surface”, “bottom surface” and the like are used in distinction to “edge surface”. If rectangular in shape or configuration, a label will comprise two opposing planar surfaces joined by four edge surfaces (two opposing pairs of edge surfaces, each pair intersecting the other pair at right angles). If circular in configuration, then the label will comprise two opposing planar surfaces joined by one continuous edge surface. The labels can be of any size and shape and as such, so can the planar and edge surfaces, e.g., thin or thick, polygonal or circular, flat or wavy, etc.

The invention is described generally with reference to the drawings for the purpose of illustrating the certain embodiments only, and not for the purpose of limiting the scope of the invention. In the drawings like numerals are used to designate like parts throughout the same.

The embodiments described by the drawings are in the context of tamper- and water-indicating labels. Each of these embodiments can be altered to be tamper- and organic solvent-indicating labels by replacing the water-soluble components with organic solvent-soluble components, and the organic solvent-soluble components with water-soluble components. Those components that are impervious to water, e.g., the top film layer, the pressure sensitive adhesive, etc., are replaced with components that are either impervious to organic solvents or impervious to both water and organic solvents.

FIG. 2A is a schematic of a multi-layer, planar ingress, tamper- and water-indicating label 20 a in which tamper-indicating label 22 is coated with water-indicating composition 21. Tamper-indicating label 22 is of any construction, and includes frangible and difficult to remove labels such as Brady Worldwide products B-351 (matte white vinyl) and B-352 (matte silver vinyl), labels that leave on the substrate to which they are attached a pattern of adhesive such as Brady products B-7575 (matte silver polyester) and B-7546 (glossy white polyester), and labels that are cleanly removed from their substrates but are irreversibly changed during removal such as those described in U.S. Pat. Nos. 5,770,283, 4,837,061, 4,994,314 and 5,135,262.

Composition 21 comprises (i) a solvent-based (i.e., non-aqueous based) binder, (ii) a non-water soluble pigment that is present at a concentration above the critical pigment to binder ratio, and (iii) dispersed water-soluble dye or pigment particles. The critical pigment to binder ratio is that ratio at which there is just enough volume of binder to fill all of the space between pigment particles such that any additional pigment results in void formation. The presence of this excess non-water soluble pigment in the composition renders the composition porous to liquid water. Typically, the excess non-water soluble pigment is present in the composition on a volume percent (vol %) basis, based on the volume of the binder, of at least 50, preferably at least 65 and more preferably at least 75, vol %. The water-soluble dye or pigment particles are present at a fairly low concentration, e.g., typically at a wt % between 1 and 20, preferably between 2 and 10 and more preferably between 4 and 8, based on the weight of the composition. One or more dyeing assistants, e.g., sodium chloride or sodium sulfate, can also be used if desired.

The color of the dye and pigment can vary to convenience and depending upon the amount and color of the pigment, the dye can be hidden to some extent until wetted. Pigments can include but are not limited to silicas, aluminas, carbonates, clays, metals, metal oxides, glasses, and solid forms of dyes, polymers and any insoluble particulates. The porous composition is sufficiently porous that water can quickly enter, yet sufficiently thin that the underlying tamper-indicating features remain operational.

The water-soluble dye or pigment is present in dispersed or particulate form. The pigment or particles are typically smaller than 100, preferably less than 50, microns to minimize visibility. Upon contact with water, the particles dissolve and the dye “blooms” thus becoming highly visible. If the dye in particulate form is too intense such that its color is objectionable, this can be moderated by adding a complementary colorant such that the color of the dye is muted or “greyed-out” until activated upon contact with water. For example, a colorant selected to give a red color upon contact with water may impart a pink color to composition 21. If a pale green colorant, e.g., dye, pigment, ink, is included in composition 21, then the observed color is of a more neutral hue.

FIG. 2B is a schematic of a multi-layer, planar ingress, tamper- and water-indicating label 20 b which is essentially of the same construction as the label of FIG. 2A except that composition layer 23 does not comprise a water-soluble dye or pigment, and it does not have to be porous (and preferably it is non-porous). Rather, label 20B comprises top layer 24 which is printed or otherwise applied as indicia to the top surface of composition 23. The indicia can be in the form of words, numbers, symbols, bar code or any other format that conveys information. Top layer 24 comprises the water-soluble dye or pigment. If it also comprises a solvent-based ink or dye, then the water-soluble dye or pigment particles can be printed as invisible indicia that appear upon contact with water. If top layer 24 comprises only water-soluble components, e.g., only the water-soluble dye or pigment particles, or the particles in combination with a water-soluble ink, then the indicia will smear upon contact with water. Standard tamper-indicating label 22 is of the same construction as that in FIG. 2A.

FIG. 2C is a schematic of a multi-layer, planar ingress, tamper- and water-indicating label 20 c which is essentially of the same construction as the label of FIG. 2A except that it further comprises top layer 25. The top planar surface of composition 21 is coated or laminated with a thin layer of crosslinked hydrophilic polymer 25. This polymer has the properties that allow it to absorb and transmit water while maintaining its integrity as a continuous film. This polymer film keeps the colorant from leaching out of composition 21 and into the substrate to which it is attached, e.g., an electronic device. The composition of this polymer can vary widely, and two such compositions are polyvinyl(alcohol) crosslinked with any suitable material, e.g., aziridine, zinc ammonium carbonate, zirconium ammonium carbonate, glyoxal (i.e., ethanediol), etc., and polyamide-epichlorohydrin type resins such as Polycup 172 available from Hercules Chemical Co. Polyvinyl(alcohol) that is super-hydrolyzed (i.e., more than 99% of the acetate groups have been converted to hydroxyl groups) such as CEVOL™ 165 available from Celanese is particularly preferred. Composition layer 21 and label 22 are of the same construction as in FIG. 2A. In operation, water comes into contact with the dye or pigment particles in the surface of layer 21, and dissolves the particles. The solubilized dye or pigment then is trapped in layer 25 staining it to produce a permanent color.

FIG. 2D is a schematic of a multi-layer, planar ingress, tamper- and water-indicating label 20 d which is essentially of the same construction as the label of FIG. 2C except that layer 21 is not porous to water. Label 20 d comprises (a) tamper-indicating label 22, (b) layer 26 that is coated over label 22, non-porous to water, and comprises (i) a solvent-soluble binder, and (ii) dispersed water-soluble dye particles, and (c) crosslinked polymer film 25 that is coated over layer 26, the film capable of absorbing and transmitting water while still maintaining its integrity as a continuous layer. In operation, water comes in contact with the dye particles in layer 26, and dissolves the dye particles. The soluble dye then is trapped in crosslinked polymer film 25 staining it to produce a permanent color.

Although the invention has been described in considerable detail by the preceding examples and reference to the drawings, this detail is for the purpose of illustration and is not to be construed as a limitation upon the spirit and scope of the invention as it is described in the appended claims. All U.S. patents, allowed U.S. patent applications and U.S. Patent Application Publications cited above are incorporated herein by reference. 

1. A planar ingress, tamper- and solvent-indicating label comprising a single layer of a solvent-indicating composition coated over a tamper-indicating label, the composition porous to solvent and comprising an organic solvent-soluble binder, pigment in excess of that necessary to fully bind with the binder, and dispersed solvent-soluble dye particles.
 2. The label of claim 1 in which the organic solvent-soluble binder
 3. The label of claim 1 in which the solvent-soluble dye is a water-soluble dye.
 4. The label of claim 1 in which the pigment is a silica, alumina, carbonate, clay, metal, metal oxide, glass or a solid form of a dye.
 5. An electronic device bearing the label of claim
 2. 6. The electronic device of claim 5 in the form of a computer, cell phone or personal digital assistant.
 7. A planar ingress, tamper- and solvent-indicating label comprising (A) a tamper-indicating label, (B) a composition (i) coated over the label, (ii) porous to solvent, and (iii) comprising an organic solvent-soluble binder and a pigment in excess of that necessary to fully bind with the binder, and (C) an ink coated over the composition and comprising a solvent-soluble dye.
 8. The label of claim 7 in which the organic solvent-soluble binder
 9. The label of claim 7 in which the solvent-soluble dye is a water-soluble dye.
 10. The label of claim 1 in which the pigment is a silica, alumina, carbonate, clay, metal, metal oxide, glass or a solid form of a dye.
 11. An electronic device bearing the label of claim
 8. 12. The electronic device of claim 11 in the form of a computer, cell phone or personal digital assistant.
 13. A planar ingress, tamper- and solvent-indicating label comprising (A) a tamper-indicating label, (B) a composition (i) coated over the label, (ii) porous to solvent, and (iii) comprising an organic solvent-soluble binder, dispersed solvent-soluble dye particles, and a pigment in excess of that necessary to fully bind with the binder, and (C) a crosslinked polymer film that can absorb and transmit solvent while still maintaining integrity as a continuous layer.
 14. The label of claim 13 in which the organic solvent-soluble binder
 15. The label of claim 13 in which the solvent-soluble dye is a water-soluble dye.
 16. The label of claim 13 in which the pigment is a silica, alumina, carbonate, clay, metal, metal oxide, glass or a solid form of a dye.
 17. An electronic device bearing the label of claim
 14. 18. The electronic device of claim 17 in the form of a computer, cell phone or personal digital assistant. 